Hi Juliey,
The Eventbrite Sync to Salesforce is built by a 3rd party developer but they have implemented these changes already. If you are receiving an error when using the connector, please let us know!
You would have received the email due to an API key that's registered to your account directly calling one of these outdated endpoints. This would often be for a custom website or integration. If you have either of these, you may need to have your developer have a look at the endpoints used and update as necessary.
Cheers